An ink jet printer typically includes a printhead and a carrier. The ink jet printhead can comprise a printhead body, nozzles, and corresponding ink ejection actuators, such as heaters on a printhead chip. The actuators cause ink to be ejected from the nozzles onto a print medium at selected ink dot locations within an image area. The carrier moves the printhead relative to the medium, while the ink dots are jetted onto selected pixel locations, such as by heating the ink at the nozzles.
In some such systems, the ink reservoir comprises a removable or separable tank, such that the tank can be separated from the printhead, and replaced or refilled, when the ink is low. The printhead components can then be re-used. In such ink tank systems, a separable fluid connection between the tank and the printhead body is needed, in contrast to systems where the printhead body is integral with the ink reservoir. The connection permits ink to flow to the nozzles from the tank, but is separable such that the ink tank can be removed when empty. The printhead assembly can also include a filter within an ink passageway leading from the ink reservoir to the nozzles, for isolating any contaminants or debris from the ejectors and nozzles.
In the industrial market, the proliferation of digital printing is underway. This proliferation provides a unique opportunity for thermal inkjet technology, due to low cost points associated with the bill of materials (BOM) and manufacturing of thermal inkjet printers. The printhead requirements for the industrial market is different and more challenging due to the non-traditional inks being used. The ink chemistries, which are solvent UV curable and latex based, are formulated to wet, penetrate and adhere to non-porous medias (examples of the various substrates are mentioned above). Solvents that are typically used generally have lower surface tension compared to water and will wet lower surface energy surfaces/substrates. Another property that the solvent system provides is the ability of the solvent to cause interfacial diffusion of ink into the substrate allowing for improved adhesion and durability. This is critical due to the non-porous nature of the various substrates used in the industry and the fact that the printed media will be subjected to various environments. Ketones and acetates such as methyl ethyl ketone (MEK) or ethyl acetate are some of the most aggressive solvents used in solvent ink formulations. Currently MEK based inks provide a significant advantage over alcohol-based inks because of its ability to wet and adhere to various plastic (polyolefin base substrates) in a variety of packaging applications/markets.